Renal blood flow transit time in the study of renal transplants

Radio-hippurate scintigraphy has been used to study renal transplant function because of its unique advantages over other noninvasive methods. Despite a great sensitivity in diagnosing the existence of a functional problem the test lacks in specificity. In an effort to differentiate between acute tubular necrosis (ATN) and graft rejection (RJ) the authors preceded hippurate scintigraphy by measurements of renal flow transit time (TT). After an intravenous injection of 8 mCi of Tc-99m-sulfur-colloid flow curves from the kidney and the abdominal aorta in 1 sec intervals for 1 min were obtained. Renal transit time was mathematically calculated and corrected for bolus and circulatory differences by dividing it with the corresponding Aortic TT (corrected Renal TT(cRTT). Radiohippuran (O-I-131-Hippurate), 150 μCi was injected subsequently and of the different computer generated parameters the 30 min net cortical residual (% of the peak) activity (Hippuran Residual Activity, HRA) was found more sensitive and reproducible for comparisons. Results of documented cases showed a statistically significant difference. Uncomplicated cases (usually on antirejection therapy) showed a tendency to increasing the cRTTs with time (not significantly) but their HRAs were significantly lower than in ATN and RJ (p< 0.001)